Squeezing the MLBPA takes priority over making GM's jobs easier. I don't see how we'll get an answer on this stuff before March, if then, since it's all tied to length of season, potential salary proration, and expanded playoffs. The owners also don't just want to concede the DH for next CBA.
I doubt roster size will expand, that was really a product of the shortened season and lack of proper spring training the second time around. So long as there's still a COVID IR you can have a taxi squad and/or more easily add AAAA types to the 40 temporarily.
I'm sure some teams legitimately don't want there to be a DH because it adds payroll too, whether competitively (15 more teams could theoretically bid for Nelson Cruz) or just creating pressure to upgrade your 5th OF or second IF bench spot by a a million or two. Even JT's value is affected (and it's a big problem for the Phillies with Cutch, potentially).